Piezo electric oscillator



1932- A. MEISSNER 1,875,087

PIEZO ELECTRIC OSCILLATOR Filed July 7, 1928 INVENTOR ALEXANDER MEISSNER A ORNE'Y Patented Aug 30, 1932 umransraras PATENT. DFFICE ALEXANDER IEIBSNEB, OI BERLIN, GERMANY, ASSIGNOB TO TELE'FUNKEN GESEIAIA- Y SGELF'I' FUR DBAETLOSE TELMRAPHIE I. 3. H. HALLESCHES, F BERLIN, GER- l IANY, A CORPORATION 01' GERMANY rmzo ELEGIBIC OSCILLATOR Application fled July 7, 1928, Serial No.

This invention relates to the piezo electric art and deals more specificall with a method of cutting quartz crystal osc' ators from the native crystal. v

Through investigations of the oscillations of a piezoelectric crystal, I have discovered that there exists in a natural quartz crystal structural planes both at an angle of 40-*50 and 60-75 approximately w1th respect'to the optical axis, and these structural planes extend substantially through the whole structure of the crystal. These structural planes are preferential planes and are characterized by the fact'that in the plane approximately 70 with respect to the optical axis the speed of propagation of sound is of the order of magnitude of 5400 meters .per second and in the structural planes which lie substantially at 48 with respect to the o tical axis of speed of propa ation of soun is 7700 meters. These wi elyvarying constants are roba'bly due to the fact that the material ying in these different planes have wide differences in the moduli of elasticity. The structure of the crystal shows that the aforesaid planes lying at angles of approximately 7 0 and approximately48 with respect to the optical axis have a crystalline structure which is unusually regular in its formation.

In accordance with the principles of this invention, therefore, a lon tudinall vibratinghcrystal plate or rod, w ich has 1ts longitu 'nal axislying in either of the aforementioned planes, exhibits particularly perfect and clear conditions of oscillations, whether used asa transmitter, or. as a controlling element, or as a receiver. Also, crystal plates or rods cut with their 'lon 'tudinal axis lying in planes at angles to t e optical axis, as

pointed out above, are-more readily excitable,

and show greater responsiveness, and also display most efliciently the henomenon common to piezo electric crysta at their natural periods.

The method which I employ in preparing crystals in accordance with this invention will be more readily understood from the following description taken in connection with the accompanying drawing in which:

1 is a diagrammatic view showing the 291,099, and In Germany July 19, 1927.

orientation of the longitudinal axis of crys Figs. 2 and 3 are perspective views of native quartz crystals having a top section which is out along each of the above mentioned preferential planes.

Referring in detail to Fig. l, OA indicates the optical axis of a native quartz crystal. PB indicates a plane at right angles to the plane of the paper and which is at an angle of 40 to 50 with respect to the optical axis OA of the native crystal. A quartz crystal oscillator. plate or rod having its longitudinal axis lyin in the plane PB and with its faces A. and l3 at right angles and parallel respectively to the lane PB as shown in Fig. 1, will have the esirable features of a crystal as explained above. It will be understood that the point along the optical axis at which the plane PB is cut is practically immaterial, for the reason that most crystals have the preferential planes of structure described above throughout their length, and that a section cut at any point along the optical axis, at the angle indicated, will exhibit the desirable efiects' described.

In the same way I have found that a plane QR lying at an angle of to with respect to the optical axis will also be a preferential plane and a crystal having the dimensions a b. as shown in Fig. 1 will also give improved results in operation either as a crystal oscillator or as a controlling element for a transmitter or receiver.

The plates 0." b" and a b as shown, of r course, are at the same time at right angles to one of the three electrical axes.

therefore intended merely to indicate theorder of magnitude of these angles and that in some cases it may be found that the prefer- 'ential plane lies-at an angle slightly displaced from the aforesaid angles.

Having thus described my invention, I claim:

1. A piezo-electric crystal element cut from a crystalline body at right angles to one of the electrical axes of said body, said body having an optical axis, said element havingan axis of symmetry and strata of crystalline material lying in planes parallel to said axis of symmetry and disposed at an angle of to inclusive with respect to the said optical axis.

2. A piezo-electric crystal element cut from a crystalline body in a'direction at right angles to one of the electrical axes of said body, said crystal havin a longitudinal axis and an optical axis am? being adapted to be stimulated electrically to produce longitudinal vibrations, said longitudinal axis lying at an angle of 60 to 75 with respect to said optical axis.

3. A piezo-electric crystal element cut from a crystalline body in a direction at right angles to one of the electrical axes of said body, said element being adapted to be stimulated electrically to vibrate mechanically, the longitudinal axis of said element lying in a plane of 60 to 75 with respect to the opti-. cal axis, said element being more readily excitable electrically and being more'responsive to electrical stimulation an piezoeelectric crystal elements of the same material and having their longitudinal axes at right an-v gles to the optical axes.

4. A piezo-electrical crystal element cut from a crystalline bod at right angles toone of the electrical axes 0 said body, said crystal having a longitudinal axis and an optical axis and being adapted to be stimulated electrically to produce longitudinal vibrations, said longitudinal axis lying at an angle of substantially, 67 16 with respect to said optical axis.

5. A'parallelopiped piano-electric element cut from a crystalline yvhavin an optical axis, and electrical axes in suci manner that two faces of said element are at ri ht angles to one of the electrical axes of sai body said element having an axis of symmetry and strata of crystalline material lying in planes parallel to said axis of symmetry, said axis of symmetry lying in a plane substantially 67 with respect to the optical axis of said crystalline body.

ALEXANDER MEISSNER. 

